Liquid crystals having negative dielectric anisotropy are not only useful for positive type displays of guest-host type liquid crystal display devices wherein the orientation direction of liquid crystal molecules is changed by adding a dichroic dye to form a color by variation of the direction of dye molecules, but also important as materials for various liquid crystal displays such as a DSM type (dynamic scattering mode type) liquid crystal display divice utilizing a phenomenon that the liquid crystal phase causes dynamic scattering by application of a voltage or the so-called DAP type display device for carrying out pleochroic display by a polarizing plate wherein double refraction of liquid crystal is utilized by controlling an inclination of the liquid crystal.
In liquid crystal substances used in the above described display devices, various physical properties are required to have a suitable value, respectively. For example, they are stable to light or heat, they show a nematic liquid crystal phase in a wide temperature range including a room temperature, and they have large negative dielectric anisotropy, etc. However, under existing circumstances, since it is impossible to satisfy all the above described requirements for physical properties by one compound, a composition composed of several compounds is used for attaining the object.
As a result of carrying out studies for obtaining excellent liquid crystal substances in view of the above described circumstances, the present inventors have attained the present invention. An object of the present invention is to provide liquid crystal substances having large negative dielectric anisotropy.